The bed of the prior application has as principal elements a support frame nested within a weigh frame but is not limited to this mechanism. The support frame is mounted on a base. The weigh frame carries a patient support. Four load beams, one mounted near each corner of the weigh frame, connect the weigh frame to the support frame. Each load beam consists of an elongated element which is fixed at one end to the support frame. The elongated element is cantilevered horizontally along the support frame and is connected at its free end by a vertical link to the weigh frame.
From time to time the support frame must be physically tilted with respect to horizontal to achieve a Trendelenburg position. The load beam measures only the component of the load that is perpendicular to the mounting plane or longitudinal axis of the elongated element that forms the principal component of the load beam. Therefore, as the support frame, and with it the load beam, is inclined from horizontal, the weight of a patient which is applied to the load beam in a direction perpendicular to horizontal will not be accurately measured by the load beam. The weight will be in error by the cosine of the angle of inclination. The greater the angle of inclination, the greater will be the error. In addition, there can be mechanical interferences at large angles of inclination that preclude accurate response of the load-sensing beams.